Natural rubber composites with high strength, modulus, water-resistance, and thermal stability, prepared with cellulose nanofibrils and sodium methacrylate

Natural rubber (NR) composite sheets consisting of TEMPO-oxidized cellulose nanofibrils (TEMPO–CNFs) and sodium methacrylate (mAANa) were prepared. An aqueous mixture of NR latex, TEMPO–CNFs, and mAANa was oven-dried; the dried material was kneaded to prepare cross-linked composite sheets. The NR/TEMPO–CNF/mAANa (100/20/11.2 by mass) sheets exhibited high tensile strengths of ∼ 23 MPa, whereas the tensile strengths of the neat NR sheets were ∼ 5 MPa. Scanning electron microscopy observations indicate that the TEMPO–CNFs formed fewer aggregates in the composite sheet containing mAANa than in the mAANa-free sheets. Thermomechanical tests indicate that the NR/TEMPO–CNF/mAANa sheets had higher storage moduli over the entire range from − 100 °C to 200 °C than the neat NR sheet. The NR/TEMPO–CNF/mAANa composite sheets exhibited hysteresis loss and permanent deformation behaviors, similar to or better than those of NR/carbon black composite sheets. Thus, the NR/TEMPO–CNF/mAANa composite sheets can be used in a similar manner as those consisting of all-carbon neutral components.